1. Field of the Invention
The present invention relates generally to sheet-fed printing press, or more precisely, to plate transfer apparatus by which the used plate around the plate cylinder is ejected and new plate to be used is transferred to the cylinder.
2. Description of the Prior Art
In sheet-fed press by offset printing technique, ink and dampening water are supplied to the plate wound around the plate cylinder to form pictures which are then printed on the sheet by way of blanket cylinder.
In work switching of pictures to be printed, the used plate must be promptly ejected and also new plate to be used must be transferred efficiently to the plate cylinder. These are premises for automatic plate exchange.
In Japanese published unexamined patent specification No. 108525/1996, new plate casing is swingably provided in narrow space between printing units and new plate is transferred to the plate cylinder by plate exchange apparatus with complicated attitude control device and plate feeder.
Also in Japanese published unexamined patent specification No. 254645/1999, apparatus is disclosed which comprises plate passage with bent portion near the plate cylinder, sucker for transferring the plate and various check means for strictly checking plate transfer.
In Japanese patent specification No. 2941598, apparatus is disclosed with thin board which is swingable around an axis and the plate is guided by the this board.
The apparatus with swingable casing occupies broad space and its construction is extremely complicated. Also the apparatus with sucker and strict check device costs high in production due to its complicated structure. Moreover the apparatus with turning axis obligates precise maneuvering and lacks swiftness in operation.
Nowadays, printing order has a tendency of so-called many sorts with small lot, consequently work exchange, namely plate exchange, is frequent. Thereafter, the apparatus for plate exchange shall be convenient in handling and be excellent in operation. In addition, the apparatus shall be small in its occupation and be easy in its process control, in consideration of adapting the apparatus not only to conventional series-type press, but also to satellite-type printing press in which printing units are provided in satellite-like manner around the common pressure cylinder. Moreover, high production cost hinders the apparatus from coming into use in printing press.